title: The human fetus preferentially secretes corticosterone, rather than cortisol, in response to intra-partum stressors.
abstract: BACKGROUND
  Fetal stress is relevant to newborn outcomes. Corticosterone is rarely quantified in human clinical endocrinology and is found at much lower concentrations than cortisol. However, fetal corticosterone is a candidate hormone as a fetal stress signal.
  
  
  OBJECTIVE
  Test the hypothesis that preferential fetal corticosterone synthesis occurs in response to fetal intra-partum stress.
  
  
  METHODS
  Cross-sectional comparison of paired serum corticosteroid concentrations in umbilical artery and vein from 300 women providing consent at admission to a General Hospital Labor and Delivery unit. Pre-term and multiple births were excluded, leaving 265 healthy deliveries.
  
  
  METHODS
  Corticosterone and cortisol concentrations determined by LC-MS/MS for umbilical cord venous (V) and arterial (A) samples and used to calculate fetal synthesis (A-V) and proportional fetal synthesis ([A-V]/V). Chart-derived criteria stratified samples by type of delivery, maternal regional analgesia, augmentation of contractions, and clinical rationale for emergent Caesarian delivery.
  
  
  RESULTS
  Cortisol concentrations were higher than corticosterone concentrations; however, the fetus preferentially secretes corticosterone (148% vs 49% proportional increase for cortisol) and differentially secretes corticosterone as fetal stress increases. Fetal corticosterone synthesis is elevated after passage through the birth canal relative to Caesarian deliveries. For vaginal deliveries, augmentation of contractions does not affect corticosteroid concentrations whereas maternal regional analgesia decreases venous (maternal) concentrations and increases fetal synthesis. Fetal corticosterone synthesis is also elevated after C-section indicated by cephalopelvic disproportion after labor, whereas cortisol is not.
  
  
  CONCLUSIONS
  The full-term fetus preferentially secretes corticosterone in response to fetal stress during delivery. Fetal corticosterone could serve as a biomarker of fetal stress.
authors.affiliation: Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Alberta, Canada. k.wynne-edwards@ucalgary.ca
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Wynne-Edwards
authors.forename: Heather E
authors.initials: HE
authors.lastname: Edwards
authors.forename: Trina M
authors.initials: TM
authors.lastname: Hancock
mesh_terms: D000293:Adolescent; D000328:Adult; D002585:Cesarean Section; D003345:Corticosterone / Q000097:blood* / Q000378:metabolism; D003430:Cross-Sectional Studies; D005260:Female; D005312:Fetal Blood / Q000378:metabolism; D005333:Fetus / Q000502:physiology*; D006801:Humans; D006854:Hydrocortisone / Q000097:blood* / Q000378:metabolism; D008297:Male; D011247:Pregnancy; D013312:Stress, Physiological; D047929:Term Birth / Q000097:blood; D014620:Vacuum Extraction, Obstetrical; D055815:Young Adult
chemical_list: D003345:Corticosterone; D006854:Hydrocortisone